Iridium Complex Exciplex Light-Emitting Element
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Solution Overview
Problem
Developing a stable and efficient light-emitting element with high emission efficiency, low power consumption, and high reliability, particularly for blue light emission, which has been challenging due to the difficulty in creating stable phosphorescent compounds with high triplet excitation energy levels.
Innovation Solution
A light-emitting element is designed using an exciplex structure comprising a first and second organic compound and a guest material, where the energy difference between the LUMO and HOMO levels of the guest material is larger than that of the organic compounds, facilitating efficient excitation energy transfer and low driving voltage, and incorporating an iridium complex with a nitrogen-containing five-membered heterocyclic skeleton for high triplet excitation energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a phosphorescent compound with high triplet excitation energy is used for blue light emission, then light emission energy is improved, but compound stability deteriorates
Solution Approach 1:
The patent employs a composite light-emitting layer containing both a phosphorescent compound (for high triplet excitation energy and blue light emission) and a fluorescent compound (for stability and additional emission pathways). This composite structure allows the system to achieve high light emission energy through the phosphorescent component while the fluorescent component provides stability and alternative emission channels, resolving the contradiction between emission energy and compound stability.
2Productivity
If the energy difference between singlet and triplet excitation energy is large, then light emission efficiency is improved, but driving voltage increases
Solution Approach 1:
The patent introduces an exciplex (excited state complex) formed between the phosphorescent and fluorescent compounds as an intermediary energy transfer system. The exciplex acts as a mediator that facilitates efficient energy transfer from the phosphorescent compound's triplet state to the fluorescent compound's singlet state, enabling high light emission efficiency while reducing the direct energy gap requirements and consequently lowering the driving voltage needed.
Solution Approach 2:
The patent optimizes the energy level parameters of both the phosphorescent and fluorescent compounds, specifically tuning the triplet excitation energy of the phosphorescent compound and the singlet excitation energy of the fluorescent compound to achieve optimal energy matching. By carefully selecting compounds with appropriate energy level differences and utilizing exciplex formation, the system achieves high emission efficiency while maintaining manageable driving voltage levels.
3Use of energy by moving object
If a nitrogen-containing five-membered heterocyclic skeleton is used in the iridium complex, then triplet excitation energy is improved, but electron-accepting property deteriorates
Solution Approach 1:
The patent combines an iridium complex with a nitrogen-containing five-membered heterocyclic skeleton (which provides high triplet excitation energy) with organic compounds that have strong electron-accepting properties. This composite approach allows the iridium complex to serve as the primary phosphorescent emitter with high triplet energy, while the accompanying organic compounds facilitate electron transport and acceptance, thereby compensating for the limited electron-accepting property of the heterocyclic skeleton alone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high emission efficiency and low driving voltage, enabling efficient light emission with reduced power consumption and improved reliability, particularly suitable for blue light emission.
Implementation Method 1
the energy difference between the LUMO and HOMO levels of the guest material is larger than that of the organic compounds, facilitating efficient excitation energy transfer
Implementation Method 2
Light emission from the triplet excited state is referred to as phosphorescence. The formation ratio of S* to T* in the light-emitting element is 1:3. In other words, a light-emitting element containing a compound emitting phosphorescence (phosphorescent compound) has higher light emission efficiency
Data Source
AI summary
Provided is a light-emitting element with high emission efficiency. The light-emitting element includes a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound, and the HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of a guest material is higher than that of the first organic compound, and the HOMO level of the guest material is lower than that of the second organic compound. The guest material has a function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound form an exciplex.